With the development of display technologies, Active Matrix Organic Light-Emitting Diode (AMOLED) display technology gradually becomes mature and AMOLED display devices are increasingly used in different display fields.
A basic driving unit in an AMOLED display device is shown in FIG. 1. The driving unit comprises two thin-film transistors (TFT) and a storage capacitor Cst to form a 2T1C structure. A scanning signal Vgate is input to a gate of a first thin-film transistor, and a data signal Vdata is input to a source of the first thin-film transistor. A drain of the first thin-film transistor is connected to a gate of a second thin-film transistor. A source of the second thin-film transistor is connected to a positive polarity power source Vdd, and a drain thereof is connected to a digital ground Vss. The storage capacitor Cst is arranged between the gate of the second thin-film transistor and the source thereof. A light-emitting diode is connected in series between the drain of the second thin-film transistor and the digital ground Vss.
In order to transmit the positive polarity power source Vdd to each sub-pixel unit, a corresponding power line should be provided. As shown in FIG. 2, in an AMOLED display device in the prior art, a mesh-shaped power lines are provided on an array substrate. The power lines are arranged in two layers. That is, horizontal power lines 10 are directly formed on a baseplate of the array substrate, and vertical power lines 20 are formed on an insulating layer (not shown in FIG. 2). The insulating layer is arranged between the horizontal power lines 10 and the vertical power lines 20. However, the mesh-shaped power lines occupy an over large layout space, which will limit a quantity of sub-pixel units, and lead to a low Pixels Per Inch (PPI) of the AMOLED display device.